Experiment: Alkylation

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  • Topic: Benzene, Alkyl, Steric effects
  • Pages : 2 (741 words )
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  • Published : May 8, 2013
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In this experiment, the synthesis of p-di-tert-butyl benzene was achieved by using the Friedel-crafts Alkylation. How the purposes were or were not accomplished
For this experiment, 0.02356 grams of p-di-tertbutyl benzene were recovered. The theoretical percent yield was 0.616 grams of the product. This gives a 38.2% yield. The product obtained were small white crystals, as expected. The product obtained was run in the IR which shows the significant peacks of the functional groups present in the compound which are C-H (sp3 and sp2) and C=C, representing the carbons in the benzene ring. Also, from the IR there are peaks at 834 cm-1 which indicates that this product is para-disubstituted. These functional groups indicate that the final product is p-di-tert-butyl benzene. Theory of the techniques

The technique used in this experiment was the Friedel-Crafts alkylation reaction, which is a type of electrophilic aromatic substitution. Friedel-Crafts alkylation involves the alkylation of an aromatic ring by an alkyl halide and a strong Lewis acid catalyst. In this reaction, t-butyl chloride, which is a tertiary halide, is reacted with AlCl3 forming a tertiary carbocation which then reacts with t-butylbenzene forming p-di-t-butylbenzene. T-butylbenzene is a type of benzene that bears an activating group –C(CH3)3; therefore, when the carbocation reacts with t-butylbenzene, it is most likely to attach to ortho or para position; however, if it is attached to the ortho position, steric hindrance will be produced. Thus, the electrophile adds para to the t-butyl group reducing steric hindrance and favoring the stability of the product. The substituent donates electron density to the benzene ring; however, the extra electron density delivered into the ring by the substituent is not equally divided over the entire ring, but it is concentrated in the ortho and para positions. These positions are the most reactive towards the electrophile formed. Tert-butyl...
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